What is the correct sequence of events along an axon that follows a membrane reaching threshold potential?1. The membrane depolarizes.2. Sodium channels open and sodium ions diffuse inward.3. The membrane repolarizes.4. Potassium channels open and potassium ions diffuse outward.A. 4, 1, 3, 2B. 2, 1, 4, 3C. 1, 2, 4, 3D. 3, 2, 4, 1
B
B. 2, 1, 4, 3 is the correct sequence of events along an axon that follows a membrane reaching threshold potential.
When the membrane potential of an axon reaches threshold, voltage-gated sodium channels open, allowing sodium ions to rush into the cell. This depolarizes the membrane potential, causing more sodium channels to open, creating a positive feedback loop that rapidly spikes the membrane potential.
Once the membrane potential reaches its peak, the voltage-gated sodium channels close, and voltage-gated potassium channels open, allowing potassium ions to rapidly diffuse out of the cell, repolarizing the membrane potential.
After this brief hyperpolarization period, the membrane potential returns to its resting state as the potassium channels close and the sodium-potassium pump works to restore the proper ion balance.
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